Hybrid electronic circuits are usually mounted inside a package which is intended to be closed by a lid. If the hybrid circuit is to operate properly, it is imperative that no impurities exist inside the package.
Thus, up to now, extraordinary precautions have been taken in the manufacture of hybrid circuits: manufacture takes place in "clean" rooms having a purified atmosphere; and the staff wear clothing and head-gear, etc. designed to maintain conditions of purity.
Proposals have been made to use a jet of washing liquid, usually alcohol, to wash the inside of a package in which a hybrid circuit is mounted before the package is closed by a lid. Such a washing operation is performed manually, takes a relatively long time and only gives very imperfect results. This insufficiency stems from the fact that the various electronic components inside a package have surfaces facing in different directions providing irregularities or nooks which are difficult for projected washing liquid to reach.